"In general it is morally legitimate to use a material agent in order to forward the well-being of a man in his personal relations in society, e.g. wearing glasses or deaf aid. If on moral grounds the unitive object of an act of coitus must be achieved without involving the procreative end, then there is nothing in principle wrong in using a material agent, for that agent is forwarding the personal relational factor essential for marriage, and good marriages are essential for society and the welfare of children."